         step-ch (chan)
         last-id (atom 0)
         gen-id #(swap! last-id inc)
-        w [{:gen-id gen-id :event-ch event-ch}]
+        w [{:gen-id gen-id
+            :event-ch event-ch}]
         root-actx (atom nil)
         vis (atom {:actxs {} ; {actx -> {:children {child-actx -> true},
                              ;           :wait-chs {ch -> [:take|:put optional-ch-name])},

      ((get run-controls (.-id (.-target (<! run-control-ch)))))
      (recur run-control-ch))))

(defn vis-init [cmds cmd-handlers]
  (let [max-inflight (atom 10)
        event-delay (atom 0)

                             ;         :first-taker-actx actx-or-nil}}.
                   :gen-id gen-id
                   :last-id (fn [] @last-id)})]
    (go-loop [num-events 0
              vis-last nil
              vis-last-positions nil]
      (when (> @event-delay 0) (<! (timeout @event-delay)))
      (when (< @event-delay 0) (<! step-ch))
      (let [[actx event] (<! event-ch)
